This is known as LEAN mapping, and there are a couple variants with similar names. The first reference I can remember for this is from Fireaxis : http://www.csee.umbc.edu/~olano/papers/lean/. Ryse seems to be based on this : http://advances.realtimerendering.com/s2012/Ubisoft/Rock-Solid%20Shading.pdf As gir wrote, it only…
A roughness map basically contains micro-normals so it definitely has to go to the same processing as the normal map. Our programmers insisted on it and it's one of the major reasons why Ryse has such good IQ and such little noise/in-surface aliasing, as you can see for yourself in the 4K PC port. Not processing and…